Unsteady Numerical Simulation of the Flow in a Direct Transfer Pre-Swirl System

2008 ◽  
Author(s):  
Fabio Ciampoli ◽  
Nicholas J. Hills ◽  
John W. Chew ◽  
Timothy Scanlon
Keyword(s):  
Discharge Coefficient ◽  
Direct Transfer ◽  
Elementary Model ◽  
Discharge Coefficients ◽  
Significant Difference ◽  
Aero Engine ◽  
Velocity Coefficient ◽  
Unsteady Numerical Simulation ◽  
Unsteady Effects ◽  
Cooling Air

Results of fully unsteady numerical simulations of the flow in a direct transfer pre-swirl system are presented and compared with previously published experimental data from an aero-engine representative rig. The conditions considered include those where strong unsteady effects were observed experimentally. Two different rig builds are considered, with the main difference being in the design of the pre-swirl nozzles. The agreement between calculation and experiment is very good in terms of nozzle and receiver hole discharge coefficients and in identifying significant unsteady effects at certain conditions. Predicted cooling air delivery temperatures are lower than those measured. This may be due to heat transfer and other effects in the rig which have not been modelled. Present unsteady results also show agreement, where appropriate, with earlier steady CFD and an elementary model. Both calculations and measurements show similar performance in terms of delivery temperature for the two different builds studied, despite significant difference in pre-swirl nozzle discharge coefficients for the two builds. The calculations indicate that this is associated with the nozzle velocity coefficient being considerably higher than the discharge coefficient in one case.

Measurement and Analysis of Flow in a Pre-Swirled Cooling Air Delivery System

2003 ◽  
Author(s):  
J. W. Chew ◽  
N. J. Hills ◽  
S. Khalatov ◽  
T. Scanlon ◽  
A. B. Turner
Keyword(s):  
Delivery System ◽  
Elementary Model ◽  
Swirl Chamber ◽  
Swirl Velocity ◽  
Measurement And Analysis ◽  
Aero Engine ◽  
Total Temperature ◽  
Velocity Coefficient ◽  
Cooling Air ◽  
Experimental Rig

Measurements and analysis for a pre-swirl cooling air delivery system are reported here. The experimental rig used is representative of aero-engine conditions, having 18 pre-swirl nozzles, 72 receiver holes, capable of speeds up to 11 000 rpm, and giving differences between total temperature upstream of the pre-swirl nozzles and relative total temperature measured in the receiver holes of up to 26K. Pressure and temperature measurements are reported. An elementary model is developed for calculation of the cooling air delivery temperature. This accounts for the pre-swirl nozzle velocity coefficient, moments on the stationary and rotating surfaces in the pre-swirl chamber, and flows through the inner and outer seals to the chamber. The model is shown to correlate the measurements well for a range of disc speeds and pre-swirl velocity to disc speed ratios.

A Method for Correlating the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

2000 ◽  
Vol 123 (2) ◽  
pp. 258-265 ◽  
Author(s):  
D. A. Rowbury ◽  
M. L. G. Oldfield ◽  
G. D. Lock
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Guide Vane ◽  
Discharge Coefficients ◽  
Nozzle Guide Vane ◽  
Aero Engine ◽  
Nozzle Guide ◽  
Film Cooling Holes ◽  
Asme Paper

An empirical means of predicting the discharge coefficients of film cooling holes in an operating engine has been developed. The method quantifies the influence of the major dimensionless parameters, namely hole geometry, pressure ratio across the hole, coolant Reynolds number, and the freestream Mach number. The method utilizes discharge coefficient data measured on both a first-stage high-pressure nozzle guide vane from a modern aero-engine and a scale (1.4 times) replica of the vane. The vane has over 300 film cooling holes, arranged in 14 rows. Data was collected for both vanes in the absence of external flow. These noncrossflow experiments were conducted in a pressurized vessel in order to cover the wide range of pressure ratios and coolant Reynolds numbers found in the engine. Regrettably, the proprietary nature of the data collected on the engine vane prevents its publication, although its input to the derived correlation is discussed. Experiments were also conducted using the replica vanes in an annular blowdown cascade which models the external flow patterns found in the engine. The coolant system used a heavy foreign gas (SF6 /Ar mixture) at ambient temperatures which allowed the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. These experiments matched the mainstream Reynolds and Mach numbers and the coolant Mach number to engine values, but the coolant Reynolds number was not engine representative (Rowbury, D. A., Oldfield, M. L. G., and Lock, G. D., 1997, “Engine-Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade,” ASME Paper No. 97-GT-99, International Gas Turbine and Aero-Engine Congress & Exhibition, Orlando, Florida, June 1997; Rowbury, D. A., Oldfield, M. L. G., Lock, G. D., and Dancer, S. N., 1998, “Scaling of Film Cooling Discharge Coefficient Measurements to Engine Conditions,” ASME Paper No. 98-GT-79, International Gas Turbine and Aero-Engine Congress & Exhibition, Stockholm, Sweden, June 1998). A correlation for discharge coefficients in the absence of external crossflow has been derived from this data and other published data. An additive loss coefficient method is subsequently applied to the cascade data in order to assess the effect of the external crossflow. The correlation is used successfully to reconstruct the experimental data. It is further validated by successfully predicting data published by other researchers. The work presented is of considerable value to gas turbine design engineers as it provides an improved means of predicting the discharge coefficients of engine film cooling holes.

Direct-Transfer Preswirl System: A One Dimensional Modular Characterization of the Flow

2003 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
High Efficiency ◽  
Momentum Balance ◽  
Geometrical Parameters ◽  
Direct Transfer ◽  
Pressure Losses ◽  
Discharge Coefficients ◽  
Effective Velocity ◽  
Rotor Disk ◽  
Absolute Frame ◽  
Cooling Air

In high-efficiency gas turbine engines, the cooling air for the high pressure turbine stage is expanded through stationary preswirl nozzles, transferred through the preswirl chamber and delivered to the blade feed holes of the rotor. By accelerating the cooling air in the direction of rotation, the total temperature relative to the rotor disk and the pressure losses occurring at the receiver hole inlet can be reduced. The discharge behavior of a direct-transfer preswirl system has been investigated experimentally for different number of receiver holes and different inlet geometries, varying axial gap widths between stator and rotor and for rotational Reynolds numbers up to Reφ = 2:3 × 106. The discharge coefficients of the preswirl nozzles are given in the absolute frame of reference while the definition of the discharge coefficients of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. A momentum balance is used to evaluate the deflection of the preswirled air entering the receiver holes. The flow in the preswirl chamber is characterized by introducing an effective velocity of the cooling air upstream of the rotor disk. The influences of geometrical parameters and operating points are reported and discussed in this paper.

Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets

2004 ◽  
Vol 126 (4) ◽  
pp. 803-808 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Frame Of Reference ◽  
Efficient Operation ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Secondary Air ◽  
Cooling Air ◽  
Actual Geometry

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to ReΦ=8.6×105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimizing capabilities depending on the orifice geometry.

Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets

2003 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Frame Of Reference ◽  
Efficient Operation ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Secondary Air ◽  
Cooling Air ◽  
Actual Geometry

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to Reφ = 8:6 × 105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimising capabilities depending on the orifice geometry.

Orifice Flow Calculation: Comparison Between Fluid Meter Applications — 6th Edition 1971, ASME PTC 19.5-2004 and ISO 5167 2003

2013 ◽  
Author(s):  
A. I. C. Hunter ◽  
R. G. Nyquist ◽  
S. Coller ◽  
J. Smith ◽  
H. Boice
Keyword(s):  
Mass Flow ◽  
Flow Measurement ◽  
Discharge Coefficient ◽  
Current System ◽  
Expansion Factor ◽  
Discharge Coefficients ◽  
Significant Difference ◽  
Orifice Flow ◽  
Small Change ◽  
Significant Mass

This paper presents a comparison between existing flow calculations that are currently in use by the authors’ company in its Test Data Reduction System (TDRS) and the latest ASME flow measurement standard. Equations for the current system are referenced from Flow Meter Applications – 6th Edition 1971 [1] and updated equations are referenced from Flow measurement ASME PTC 19.5-2004 [2]. Comparisons were made between mass flow, expansion factor and orifice discharge coefficient calculations. The equations for mass flow and expansion remained unchanged between versions; however a variation in results exists between orifice discharge coefficients. For a diameter ratio, β range of 0.4 to 0.7, the updated 2004 equation for discharge coefficient provides a relatively small change over the 1971 equation. The 2004 equation was also found to be less sensitive to changes in pipe diameter and Reynolds number. A comparison between the ISO 5167 2003 and PTC 19.5-1971 flow calculations was also done. There was a significant difference in the calculation of expansion factor using ISO 5167 2003, which resulted in a significant mass flow variation between the two flow measurement standards.

Direct-Transfer Preswirl System: A One-Dimensional Modular Characterization of the Flow

2005 ◽  
Vol 127 (2) ◽  
pp. 383-388 ◽  
Author(s):  
M. Dittmann ◽  
K. Dullenkopf ◽  
S. Wittig
Keyword(s):  
High Efficiency ◽  
Momentum Balance ◽  
Geometrical Parameters ◽  
Direct Transfer ◽  
Pressure Losses ◽  
Discharge Coefficients ◽  
Effective Velocity ◽  
Rotor Disk ◽  
Absolute Frame ◽  
Cooling Air

In high-efficiency gas turbine engines, the cooling air for the high-pressure turbine stage is expanded through stationary preswirl nozzles, transferred through the preswirl chamber, and delivered to the blade feed holes of the rotor. By accelerating the cooling air in the direction of rotation, the total temperature relative to the rotor disk and the pressure losses occurring at the receiver hole inlet can be reduced. The discharge behavior of a direct-transfer preswirl system has been investigated experimentally for different number of receiver holes and different inlet geometries, varying axial gap widths between stator and rotor and for rotational Reynolds numbers up to Reϕ=2.3×10 6. The discharge coefficients of the preswirl nozzles are given in the absolute frame of reference while the definition of the discharge coefficients of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. A momentum balance is used to evaluate the deflection of the preswirled air entering the receiver holes. The flow in the preswirl chamber is characterized by introducing an effective velocity of the cooling air upstream of the rotor disk. The influences of geometrical parameters and operating points are reported and discussed in this paper.

scholarly journals Discharge Coefficients of Cooling Holes With Radiused and Chamfered Inlets

1991 ◽  
Author(s):  
N. Hay ◽  
A. Spencer
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Practical Interest ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Discharge Coefficients ◽  
The Subject ◽  
Cooling Air

The flow of cooling air within the internal passages of gas turbines is controlled and metered using orifices formed of holes in discs and casings. The effects of inlet radiusing and chamfering of these holes on the discharge coefficient forms the subject of this paper. Experimental results for a range of radiusing and chamfering ratios for holes of different length to diameter ratios are presented covering the range of pressure ratios of practical interest. The results indicate that radiusing and chamfering are both beneficial in increasing the discharge coefficient. Increases of 10–30% are possible. Chamfered holes give the more desirable performance characteristics in addition to being easier to produce than radiused holes.

Discharge Coefficients of Cooling Holes With Radiused and Chamfered Inlets

1992 ◽  
Vol 114 (4) ◽  
pp. 701-706 ◽  
Author(s):  
N. Hay ◽  
A. Spencer
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Practical Interest ◽  
Performance Characteristics ◽  
Experimental Results ◽  
Discharge Coefficients ◽  
The Subject ◽  
Cooling Air

The flow of cooling air within the internal passages of gas turbines is controlled and metered using orifices formed of holes in disks and casings. The effects of inlet radiusing and chamfering of these holes on the discharge coefficients forms the subject of this paper. Experimental results for a range of radiusing and chamfering ratios for holes of different length-to-diameter ratios are presented covering the range of pressure ratios of practical Interest. The results indicate that radiusing and chamfering are both beneficial in increasing the discharge coefficient. Increases of 10–30 percent are possible. Chamfered holes give the more desirable performance characteristics in addition to being easier to produce than radiused holes.

Influence of Labyrinth Clearance on the Flow of Rotating Orifices in a Parallel Labyrinth-Orifice System

2020 ◽  
Author(s):  
Jie Wang ◽  
Shuiting Ding ◽  
Tian Qiu ◽  
Ziqiang Gao
Keyword(s):  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Labyrinth Seal ◽  
Chamber Wall ◽  
Flow State ◽  
Aero Engine ◽  
Air System ◽  
Secondary Air ◽  
Cooling Air

Abstract Orifices, especially rotating orifices, are an important flow element of the secondary air system in a modern aero-engine, and their discharge coefficient depends on the geometry, the operating point and the surrounding environment. The influence of Reynolds number, pressure ratio, rotational speed, inlet chamfer, inclination angle, length-to-diameter ratio, etc. on the discharge coefficient of rotating orifices under the assumption of room temperature and adiabatic has been reported in many literatures. However, the rotating speed, the temperature of the gas in the front and rear chambers of rotating orifices and the temperature of the chamber wall change continuously during the actual operation of the engine, especially during the acceleration and deceleration of the engine, which will cause deformation of the chamber wall and the rotating components, resulting in a large change in the labyrinth seal clearance on the periphery of the rotating orifice disk. Although the change of the seal clearance can be evaluated by some methods, it still has a crucial influence on the fluid flow in the front cavity of rotating orifices, which may affect the discharge coefficient of rotating orifices, thereby affecting the amount of cooling air flowing through rotating holes. Therefore, the knowledge of the influence of labyrinth seal clearance should be considered into the discharge coefficient of rotating orifices, which is essential for a reasonable distribution of the cooling air in the second air system under various working conditions and ensures the safety and reliability of the aero-engine in all-inclusive line. This paper presents the relationship between the discharge coefficient of rotating orifices and theoretical velocity ratio in the relative frame of reference (U/Wax) under different labyrinth seal clearance conditions, which is based on the study of the flow state in the front chamber of rotating orifices under different seal clearances, rotating speeds and pressure ratios. The results indicate that with the increase of the labyrinth seal clearance on the periphery of the rotating orifices disk, the discharge coefficient of rotating orifices decrease under the condition of small velocity ratio, while the discharge coefficient is almost unchanged under the large velocity ratio. Comparing the flow field structure and velocity field under the condition of different labyrinth seal clearances, the same pressure ratio and the same velocity ratio, the reasons for the influence of labyrinth seal clearance on the discharge coefficient of rotating orifices are analyzed.

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